Here's a super fast and effective way.
Spray model in Army Painter Leather Brown (or black and then use Foundry paint colour Dusky Flesh - pot 6B). Then apply army painter DARK tone all over.
Spray matt....finished.
VERY fast and an excellent result IMO. If you have scads of mahdists to paint I'd seriously consider this method. You can very nicely fiddle around with the other Foundry paint browns to get different shades of skin colour. The AP dark tone really gives them a good 'dark' shading that provides a 'richness' to the final figure for very little effort.
(https://abyssiniancrisis.files.wordpress.com/2016/01/img_0572-001.jpeg)
See more examples here.
https://abyssiniancrisis.wordpress.com/category/resources/miniatures/
...and here are some plastic Perry's painted that way also.
(https://agrabbagofgames.files.wordpress.com/2015/03/p1080204.jpg?w=853&h=480)
...more here
https://agrabbagofgames.wordpress.com/tag/berbers/
Happy W